SpeechToText and TextToSpeech Sample App:

This sample project use RecognizerIntent to make Speec To Text (STT) for Six Langaues (En,Ar,Fr,De,Es,Ru), you could read more about RecognizerIntent from here:

https://developer.android.com/reference/android/speech/RecognizerIntent.html

You could use Google TextToSpeech to convert the result to voice or type your text, you could read more about TextToSpeech from here:

https://developer.android.com/reference/android/speech/tts/TextToSpeech.html

If you need more powerfull solution for SpeechToText, you might use Google Cloud Speech API:

https://cloud.google.com/speech/

From my expericne with RecognizerIntent, it give an accurate result in Online Mode if your voice is clear.

In offline it have many cons:

1. The result is not accurate.

2. Can't recognize all languases.

Google Text Speech doesn't support Arabic language, so you might use library like iSpeech:

https://www.ispeech.org/developers/android

Useful links:

1. Google Text to Speech
2. Android Hive
3. Table of lable culture names